Support Using ScopedFeatureList in BrowserTest

content/public/test/browser_test_base.cc

 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "content/public/test/browser_test_base.h"
 
 #include <stddef.h>
 
 #include "base/bind.h"
 #include "base/command_line.h"
@@ skipping 222 matching lines @@
   SetUpInProcessBrowserTestFixture();
 
   // At this point, copy features to the command line, since BrowserMain will
   // wipe out the current feature list.
   std::string enabled_features;
   std::string disabled_features;
   if (base::FeatureList::GetInstance())
     base::FeatureList::GetInstance()->GetFeatureOverrides(&enabled_features,
                                                           &disabled_features);
   if (!enabled_features.empty())
-    command_line->AppendSwitchASCII(switches::kEnableFeatures,
-                                    enabled_features);
+    command_line->ReplaceSwitchASCIIForTest(switches::kEnableFeatures,
+                                            enabled_features);

[Ilya Sherman, 2017/05/16 06:43:32]

Hmm, shouldn't we extend the switch, rather than replacing it entirely?  That
is, if the switch already specifies some values, I thought we wanted to respect
those values (unless they were specifically overridden) -- no?

   if (!disabled_features.empty())
-    command_line->AppendSwitchASCII(switches::kDisableFeatures,
-                                    disabled_features);
+    command_line->ReplaceSwitchASCIIForTest(switches::kDisableFeatures,
+                                            disabled_features);
 
   // Need to wipe feature list clean, since BrowserMain calls
   // FeatureList::SetInstance, which expects no instance to exist.
   base::FeatureList::ClearInstanceForTesting();
 
   base::Closure* ui_task =
       new base::Closure(
           base::Bind(&BrowserTestBase::ProxyRunTestOnMainThreadLoop,
                      base::Unretained(this)));
 
@@ skipping 149 matching lines @@
   if (mojo_rules.empty())
     return;
 
   mojom::NetworkServiceTestPtr network_service_test;
   ServiceManagerConnection::GetForProcess()->GetConnector()->BindInterface(
       mojom::kNetworkServiceName, &network_service_test);
   network_service_test->AddRules(std::move(mojo_rules));
 }
 
 }  // namespace content